Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:1.4.1.2 (
glutamate dehydrogenase
)
4,380
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
A high concentration of ammonium (NH
4
+
) as the sole source of nitrogen in the growth medium often is toxic to plants. The nitrate transporter
NRT1
.1 is involved in mediating the effects of NH
4
+
toxicity; however, the mechanism remains undefined. In this study, wild-type Arabidopsis (
Arabidopsis thaliana
Columbia-0 [Col-0]) and
NRT1
.1
mutants (
chl1-1
and
chl1-5
) were grown hydroponically in NH
4
NO
3
and (NH
4
)
2
SO
4
media to assess the function of
NRT1
.1 in NH
4
+
stress responses. All the plants grew normally in medium containing mixed nitrogen sources, but Col-0 displayed more chlorosis and lower biomass and photosynthesis than the
NRT1
.1
mutants in (NH
4
)
2
SO
4
medium. Grafting experiments between Col-0 and
chl1-5
further confirmed that NH
4
+
toxicity is influenced by
NRT1
.1. In (NH
4
)
2
SO
4
medium,
NRT1
.1 induced the expression of NH
4
+
transporters, increasing NH
4
+
uptake. Additionally, the activities of glutamine synthetase and glutamate synthetase in roots of Col-0 plants decreased and soluble sugar accumulated significantly, whereas pyruvate kinase-mediated glycolysis was not affected, all of which contributed to NH
4
+
accumulation. By contrast, the
NRT1
.1
mutants showed reduced NH
4
+
accumulation and enhanced NH
4
+
assimilation through glutamine synthetase, glutamate synthetase, and
glutamate dehydrogenase
. Moreover, the up-regulation of genes involved in ethylene synthesis and senescence in Col-0 plants treated with (NH
4
)
2
SO
4
suggests that ethylene is involved in NH
4
+
toxicity responses. This study showed that NH
4
+
toxicity is related to a nitrate-independent signaling function of
NRT1
.1
in Arabidopsis, characterized by enhanced NH
4
+
accumulation and altered NH
4
+
metabolism, which stimulates ethylene synthesis, leading to plant senescence.
...
PMID:NRT1.1-Related NH
4
+
Toxicity Is Associated with a Disturbed Balance between NH
4
+
Uptake and Assimilation. 3033 53
